Onun bize anlattığı şakayı anlayamadım.
 - I couldn't catch on to the joke he told us.
O onun ne dediğini anlayabiliyor gibi görünmüyor.
 - She doesn't seem to be able to catch on to what he is saying.
He didn't have to explain; I caught on right away.
It's a crummy idea, and I certainly hope it does not catch on.
... things, would you advise it? Will it catch on? ...